Fuze



Aug. 25, 1959 D. STATHAM FUZE 3 Sheets-Sheet 1 Filed NOV. 30, 1946,

QN Mk INVENTOR LOU/8 D. STATHAM ATT RNEY Aug 25, 1959 0Q STATHAM FUZE 3 Sheets-Sheet 3 Filed Nov. 30, 1943 INVENTOR LOU/.5 0. STA THAM United States Patent FUZE Louis D. Statham, Beverly Hills, Calif., assignor to the United States of America as represented by the Secretary of the Navy Application November 30, 1943, Serial No. 512,384

7 Claims. (Cl. 102-702) This invention relates to fuzes and has particular reference to a magnetic fuze of novel construction which is operable upon contact with a ferrous metal object or upon movement of the fuze adjacent the object. The new fuze is sensitive and positive in operation, is compact in construction, and may be handled with safety. The fuze is particularly adapted for use with antisubmarine bombs, although it is to be understood that the invention is not limited to fuzes for this use.

One object of the invention resides in the provision of a bomb fuze operable to detonate the bomb when the fuze contacts or moves near a ferrous or magnetic metal.

Another object of the invention is to provide a magnetic fuze having a magnet associated with a wire coil, so that when the fuze is moved adjacent a ferrous metal object, it is exploded by the electrical energy developed in the coil due to the change in the magnetic field caused by the metal.

A further object of the invention is to provide a magnetic fuze for use with antisubmarine bombs, which is operable to explode the bomb only when it contacts or moves close to a ferrous or magnetic portion of the submarine.

Still another object of the invention resides in the provision of a bomb fuze of the character described for use against submarines, which is safe to handle and explodes upon contact with a submarine but not from other causes, such as jarring, pressure, acceleration, deceleration, nearby explosions, contact with nonferrous objects, etc.

An additional object of the invention is to provide a self-arming, magnetic fuze for use with antisubmarine bombs, which is compact in construction, may be handled with safety, and has relatively few moving parts. I Bomb fuzes of various forms have been proposed heretofore for use against submarines, but these fuzes are not entirely satisfactory. One form of bomb fuze proposed heretofore is the inertia type fuze in which the explosion is caused by deceleration of the bomb. Fuzes of this type are objectionable for the reason that they may be armed by acceleration or deceleration from causes other than striking the target, as, for example, by striking the water. Consequently, it has been found necessary to construct the fuze so that it remains unarmed until the bomb has reached its terminal velocity. Generally, such fuzes are maintained unarmed by the use of a hydrostatic pressure device. In other words, when the bomb reaches a certain depth, the water pressure automatically arms the fuze so that the bomb is exploded upon any subsequent deceleration. The operation of such fuzes requires a hydrostatic pressure existing at a depth which is reached by the bomb only after it has attained its terminal velocity in falling through the water. This depth has been found to be approximately 35 feet and precludes the possibility of use of the bomb against submarines cruising on the surface or at a depth less than 35 feet.

The fuze of the present invention overcomes the abovementioned difi'iculty, since it includes a means for arming the fuze as it passes through the air or water. Thus, the fuze may be arranged to arm before it strikes the water so that it is adapted to explode immediately on contacting or moving near any ferrous or magnetic object in the water.

Another type of bomb fuze developed heretofore is intended to fire at certain hydrostatic pressures or upon contacting any kind of surface, such as the bottom of the ocean. Fuzes of this type are objectionable because, if the craft used to deliver the submarine attack is equipped with echo-ranging equipment, the ineffective explosions caused by the fuzes render such equipment useless for appreciable periods of time. With the fuze of my invention, detonation cannot occur unless and until the bomb strikes the submarine or other ferrous or magnetic object whereby the echo-ranging equipment may be used continually until the submarine is destroyed.

A fuze made in accordance with my invention requires relatively few moving parts which are necessary only for safety purposes, the fuze per se having no moving parts. It has been found that my new magnetic fuze is effective against a submarine even if the bomb containing the fuze should fall upon a wooden deck or other nonferrous part of the submarine, since the water action causes the bomb to be washed off the deck with the result that the magnetic action of the fuze, as it contacts or moves adjacent some ferrous part of the submarine, detonates the bomb. Because of its magnetic operation, the new fuze has the advantage that it eliminates the possibility of the bomb being exploded when it contacts the surface of the water, particularly when the bomb is dropped from aircraft flying at a high altitude or in dive bombing.

For a better understanding of the invention, reference may be had to the accompanying drawings in which:

Fig. 1 is a side elevational view of an antisubmarine bomb embodying one form of the new fuze;

Fig. 2 is an enlarged, side elevational view of the fuze shown in Fig. 1;

Figs. 3 and 4 are schematic views illustrating the principle of the operation of the fuze;

Fig. 5 is an enlarged, longitudinal sectional view of the fuze;

Fig. 6 is a front view of the fuze;

Fig. 7 is a sectional view on the line 77 in Fig. 2;

Figs. 8 and 9 are front and side views, respectively, of the end cap of the fuze;

Figs. 10 and 11 are plan and front views, respectively, of a safety gate for the fuze;

Fig. 12 is a longitudinal sectional view of an insulating cylinder in the fuze, and

Fig. 13 is a rear elevational view of the insulating cylinder.

Referring to Fig. 1 in the drawings, the numeral 15 designates an antisubmarine bomb having a nose portion 16 which is recessed to receive the fuze, shown generally at 17. The fuze 17 projects forwardly from the nose of the bomb and is provided with an arming wire 18 adapted to be secured to part of an aircraft from which the bomb is launched, as will be described in greater detail presently.

The operating principle of the invention is illustrated schematically in Figs. 3 and 4. As there shown, a bar magnet 20 is wrapped with a series of turns of wire forming a coil 21 near one end of the magnet. The ends of the coil 21 are connected by wires 22 across an electrical squib or detonator 23. It will be observed (Fig. 3) that the lines of magnetic force from the magnet normally pass through the air from one pole of the magnet to the other in a substantially symmetrical pattern. When one end of the magnet 20 is moved against or adjacent to a ferrous object B (Fig. 4), the flux pattern of the magnet 3 is changed so that part of the lines of magnetic force new pass through the ferrous object. The resulting alteration of the field of the magnet causes an electromotive force to be generated in the coil 21 which produces an electric current sufficient to energize and operate the detonator 23. It has been found that electrical energy sufficient to operate the detonator is generated in this manner regardless of the angle of incidence of the ferrous ob ect B.

The fuze 17 comprises a hollow, cylindrical, permanent magnet 20a seated at its rear end against a cylindrlcal cap 25. A metal bobbin or spool 26, which may be made of soft steel, is mounted on the front end of the magnet. Intermediate its ends, the spool 26 has an external, annular recess for receiving a coil of wire 21a, the front end of the spool being beveled, as shown at 28, to form a recess on its inner radius. An annular plug 29 extends into the front end of the spool 26 and has a beveled head which fits closely against the beveled surface 28 of the spool. The plug 29 is threaded into the front end of a frame in the form of a brass cylinder 30, as shown at 31, the rear end of the cylinder being threaded into the cap 25, as shown at 32. The cylinder 30 extends through the magnet 20a with a substantial clearance and is disposed in concentric relation to the magnet. A pin 33 on the spool 26 projects inwardly into a longitudinal slot 30a in the front end portion of cylinder 30 so as to prevent rotation of the spool relative to the cylinder. Thus, the entire unit is held together, as shown, by screwing the cylinder 30 into cap 25, inserting the cylinder through magnet 20a, and sliding the spool 26 over the protruding end of the cylinder. When the plug 29 is screwed mm the front end of cylinder 30, the entire unit may be drawn snugly together. However, the spool 26 is provided wlth a rearwardly extending boss 34 which fits between the magnet 20a and the cylinder 30 so as to malntam these parts in spaced relation. D

The spool 26 is provided with an lnsulatmg sleeve 36 extending radially inwardly from the bottom of coil 21a into the slot 30a in the front end portion of cylinder 30. The ends 37 and 38 of coil 21a are led through sleeve 36 into the interior of cylinder 30 and are connected to the squib or detonator 23, as will be described ingreater detail presently. Surrounding the spool 26 1s a thin metal protective ring 40 having an outwardly extending flange 40a on its front end. The ring 40 is connected to the spool 26 by screws 41 and serves to retain the magnet 20a and coil 21a in place, in addition to serving another function which will be described presently.

A cylindrical insulator 43 is disposed loosely m the cylinder 30 in concentric relation thereto. The insulator 43 is closed at its rear end, as shown at 44, and has a pair of longitudinal, diametrically opposed slots 45 and 46 in its outer surface. Two holes 47 are formed in the bottom of each of the slots 45, 46 and communicate with the central hollow portion of the insulator. The insulator is provided with a pair of contact springs 48 mounted in diametrically opposed relation in the slots 45 and 46, and with a similar pair of contact springs 48a mounted in the slots 45 and 46 in front of the springs 48. The springs 48 and 48a have contact points 49 and 49a, re spectively, extending into the insulator 43 through the adjacent openings 47. Thus, the springs 48 and 48a provide two pairs of opposed switch contacts 49 and 49a, respectively, in the insulator. The contact springs may be secured in the insulator slots by any suitable means, such as screws 50.

The ends of wires 37 and 38, leading from the coil 21a, are connected to the contact springs 48 and 48a, respectively, in slot 46, and the contact springs 48 and 48a in slot 45 are connected through wires 37a and 38a, respectively, to the detonator or squib 23, which is seated in a recess in the rear end portion of insulator 43. A passage 52 (Fig. 13) is provided in the insulator between the squib 23 and the adjacent slot 45 to receive the wires 37a and 38a. It will be observed that the front end of 4 insulator 43 has an extension 43a which is seated against the rear face of plug 29, while the rear end of the insulator is seated in a central recess in cap 25.

A contact rod 54 extends longitudinally through the hollow interior of insulator 43 and projects rearwardly through axial openings in the closed end 44 of the insulator and the cap 25. At its front end, the rod 54 extends into a central opening in an axial insert 55 in the plug 29, the opening in the insert communicating directly with an enlarged threaded recess 55a in the insert. A cylindrical insulator tube 56 is secured to the central portion of rod 54 and carries two longitudinally spaced contact rings 57 and 58 which are normally disposed to the rear of the contacts 49 and 49a, respectively. Near its front end, the rod 54 is provided with an outwardly extending flange 59, and seated on the front face of flange 59 is a rubber gasket 60 through which the rod 54 projects. A spring 61 is coiled around the rear end portion of rod 54 and is compressed between the rear end 44 of the insulator and the rear end of the insulator tube 56.

At the front end of the fuze is an arming cap indicated generally at 63. Various forms of arming devices may be employed, but for illustrative purposes I have shown an arming device comprising a transverse plate 64 mounted within the cap 63 by means of screws 65. A shaft 66 extends through the central portion of plate 64 and is keyed to a gear wheel 67 disposed between the plate 64 and the cap 63. The shaft 66 is threaded at its rear end, as shown at 68, and is screwed into the threaded recess 55a in the insert 55. Intermediate its ends, the shaft 66 has an external flange 66a, and between the flange and the plate 64 are a cover plate 69 and a gear 70. The plate 69 and gear 70 are rotatable freely on shaft 66 but are pinned together by means of studs 71. A second shaft 73 is mounted in plate 64 in offset relation to the shaft 66 and carries at its opposite ends a pair of gears 74 and 75 which mesh with the gears 67 and 70, respectively. The gears 74 and 75 are identical and have the same number of teeth, and the gears 67 and 70 are also identical except that gear 67 has one more tooth than gear 70. A holding pin 76 is mounted on the cover plate 69 and extends into insert 55 and plug 29 to hold the plate portion of the planetary gear system stationary.

A set of air fins 78 is mounted externally of cap 63 by means of the screws 65 and carries an external flange 79 which is normally in spaced, opposed relation to the flange 40a. The flanges 40a and 79 are provided with aligned openings for receiving a safety pin 80 which locks the fins 78 against rotation. Mounted in the space between the flanges 40a and 79 is a de-icing mechanism which comprises a rubber ring 81 and a metal ring 82 surrounding the closure line between the cap 63 and the spool 26. The metal ring 82 is drawn tightly around the rubber ring and is held together at its ends 83 by means of the arming wire 18, which also locks the fins 78 against rotation.

The cap 25 is externally threaded intermediate its ends, as shown at 86, whereby the fuze may be screwed into the nose of the bomb. As pointed out heretofore, the cap is provided with a central recess for receiving the rear end 44 of the insulator in which the squib 23 is mounted. The squib 23 projects rearwardly beyond the end of the insulator and into a recess 87 in the adjacent wall of the cap. At its rear end portion, the cap 25 is provided with an externally threaded boss 25a which is slotted transversely, as shown at 88, the slot extending diametrically across the boss (Fig. 9). A passage 89 in the cap 25 connects the squib recess 87 with slot 88.

A slide or safety gate 90 is seated in the slot 88 at one end thereof. As shown particularly in Figs. 10 and 11, the gate 90 is recessed at 91 to receive the rear end of rod 54 when the gate is in its armed position, as will be described in greater detail presently. An opening 92 extends through the slide 90 parallel to rod 54 and is adapted to receive an explosive charge, such as mercury fulminate (not shown), the opening 92 being normally off set radially from passage 89. On each side of the opening 92 is a small chamber 93 in the gate which receives a compression spring 94, the outer ends of the springs 94 bearing against the inner wall of a sleeve 95 threaded on the boss 25a (Fig. 7), whereby the springs 94 urge gate 90 toward the central portion of slot 88. The gate 90, however, is normally held in a retracted position at one end of slot 88 by the rod 54, as shown inrFig. 7. The sleeve 95 contains a brass end plate 96 which is positioned axially in the sleeve by a thin metal ring 97 disposed between the plate 96 and a disc 98 closing the rear end of the sleeve. The disc 98 is secured in the sleeve 95 in any desired manner, as by crimping the rear end of the sleeve over the disc, as shown at 95a. The end plate 96 is held by ring 97 against the rear face of the cap boss 25a so as to retain the gate 90 in slot 88. The plate 96 is provided with an opening 99 which is filled with a tetryl lead charge, the opening 99 being aligned with the squib passage 89 and communicating with chamber 100 defined by the end plate, the ring 97 and the disc 98. It will be observed that the slide 90 in its normal position (Fig. 5) blocks the opening 99 from the squib passage 89 so that any accidental explosion of the squib cannot be communicated to the usual booster charge of tetryl (not shown) in chamber 100.

In the use of the new fuze, it is mounted in the bomb by screwing the threaded portion 86 of cap 25 into an internally threaded receptacle in the nose of the bomb. The safety pin 80 and the arming wire 18 remain in position until the bomb is placed in the bomb rack or other mechanism from which it is to be released. The pin 80 is then removed and the arming wire 18 is attached to the mechanism from which the bomb is to be dropped. When the bomb is released, the arming wire 18 is withdrawn from the ends 83 of band 82 which, under the expansive force of ring 81, snaps off and breaks any ice or foreign material surrounding it, whereby the fins 78 are free to rotate.

When the bomb is released, the cap 63 is held in position by shaft 66 which is screwed into the insert 55. As the bomb starts to fall, the fins 78 commence to rotate and carry the plate 64 with them. Thus, the planetary gears mounted on shaft 73 rotate around the centrally mounted gears 67 and 70. Since the latter gears have an unequal number of teeth, this rotation causes shaft 66 to rotate slowly so that it is gradually screwed out of the insert 55. When the shaft 66 is withdrawn from insert 55, the entire cap assembly drops off, and the rod 54, which was previously bearing against the rear end of shaft 66, is snapped forward by the compression spring 61, thereby arming the fuze.

In the armed position of the fuze, the rubber ring 60 is held tightly against the insert 55 by spring 61 to prevent any water from entering the insulator 43 and short circuiting the electrical contacts. Also, with the rod 54 in its forward position, its contact rings 57 and 58 engage the contact springs 49 and 49a, respectively, so as to connect the coil 21a to squib 23 through wires 37, 38 and 37a, 3811. As the rod 54 is moved forwardly under the action of spring 61, its rear end disengages the gate 90, whereupon the gate is moved by springs 94 toward the opposite end of slot 88 until the outer end of recess 91 engages the rod. The gate is nowin its armed position in which its opening 92 is in alignment with the squib passage 89 and the tetryl charge in the opening 99. When the bomb enters the water and the spool 26 is moved near or into contact with a ferrous metal object, the field of the magnet 20a changes due to the fact that the ferrous metal object oifers less resistance than the surrounding water to the lines of force between the poles of the magnet. As a result, an electromotive force is induced in the coil 21a which causes a current to flow through the coil, the wires 37, 38, contacts 49, 49a, rings 57, 58, the opposed contacts 49, 49a, and wires 37a, 38a, to the detonator 23. The detonator is thus fired and the explosion passes through passage 89 and fires the mercury fulminate in opening 92, which, in turn, explodes the tetryl in opening 99 and the booster in chamber 100.

The fuze in the form illustrated may be used to particular advantage in bombs adapted to be launched from airplanes, because the fuze is armed by the action of the fins 78 as the bomb falls through the air. Accordingly, the fuze is operable to detonate the bomb immediately upon striking or moving near a ferrous metal object, whether the object is on the surface of the water or submerged. It will be apparent that the fuze could be used with bombs which are dropped from the deck of a surface craft, by designing the arming cap 63 so that it is released after it passes through a certain depth of water. This can easily be accomplished by determining the number of turns the fins 78 will make in passing through a given depth of water. Also, the fuze could be provided with a pressure arming device in place of the propeller arming device 78 and still retain its most important advantage when used from surface craft, that is, the advantage of preventing any explosion which would interfere with the echo-ranging equipment, unless a ferrous object is actually encountered.

I claim:

1. A magnetic bomb fuze comprising a tubular magnet, a coil of wire mounted on the magnet, a tubular insulator in the magnet, an electrically operable detonator, means for electrically connecting the coil to the detonator including a pair of normally open contacts in the insulator, an operating rod in the insulator having a bridging member normally spaced from the contacts, an arming device, and means under control of the arming device for operating the rod to engage the bridging member with said contacts, whereby the presence of a metallic object adjacent the magnet alters the magnetic field thereof to cause an electro-motive force to be generated in the coil" and thereby operate the detonator.

2. A magnetic bomb fuze comprising a tubular magnet, a coil of wire mounted on the magnet, a tubular insulator in the magnet, an electrically operable detonator, means for electrically connecting the coil to the detonator including a pair of normally open contacts in the insulator, an operating rod in the insulator having a bridging member normally spaced from the contacts, an arming device, means under control of the arming device for operating the rod to engage the bridging member with said contacts, whereby the presence of a metallic object adjacent the magnet alters the magnetic field thereof to cause an electro-motive force to be generated in the coil and thereby operate the detonator, a firing train leading from the detonator, a safety gate in the firing train for maintaining said train normally unarmed, and means under control of said rod for moving the gate to an armed position for arming said firing train.

3. A magnetic bomb fuze comprising a tubular magnet, a spool on one end of the magnet, a coil on the spool, a tubular frame extending through the magnet and into the spool, the magnet and the frame being maintained in concentric spaced relation by the spool, a cap secured on one end of the frame and engaging the adjacent end of the magnet, an arming device mounted on the opposite end of the frame, a tubular insulator in the frame,

an electrically operable detonator, means for electrically connecting the coil to the detonator and including a pair of normally open contacts in the insulator, an operating rod in the insulator having a bridging member and being slidable in the cap, said arming device normally holding the rod in position to maintain the bridging member out of engagement with said contacts, and means under control of said arming device for actuating the rod to move the bridging member into engagement with the contacts, whereby the presence of a metallic object adjacent the magnet alters the magnetic field thereof to cause an electro-motive force to be generated in the coil and thereby operate the detonator.

4. A magnetic bomb fuze comprising a tubular magnet, a spool on one end of the magnet, a coil on the spool, a tubular frame extending through the magnet and into the spool, the magnet and the frame being maintained in concentric spaced relation by the spool, a plug threaded on one end of the frame and engaging the spool, a cap secured on the opposite end of the frame and engaging the adjacent end of the magnet, the plug being adapted to be tightened on the frame to draw said cap, magnet and spooltogether against the plug, an arming device mounted on the plug, a tubular insulator in the frame, an electrically operable detonator, means for electrically connecting the coil to the detonator and including a pair of normally open contacts in the insulator, an operating rod in the insulator having a bridging member and being slidable in the cap, said arming device normally holding the rod in position to maintain the bridging member out of engagement with said contacts, and means under control of said arming device for actuating the rod to move the bridging member into engagement with the contacts, whereby the presence of a metallic object adjacent the magnet alters the magnetic field thereof to cause an electro-motive force to be generated in the coil and thereby operate the detonator.

5. A magnetic bomb fuze comprising a tubular magnet, a spool on one end of the magnet, a coil on the spool, a tubular frame extending through the magnet and into the spool, the magnet and the frame being maintained in concentric spaced relation by the spool, a cap secured on one end of the frame and engaging the adjacent end of the magnet, an arming device mounted on the pposite end of the frame, a tubular insulator in the frame, an electrically operable detonator, means for electrically connecting the coil to the detonator and including a pair of normally open contacts in the insulator, an operating rod in the insulator projecting at one end through the cap and having a bridging member in the insulator, said arming device normally holding the rod in position to maintain the bridging member out of engagement with said contacts, means under control of said arming device for actuating the rod to move the bridging member into engagement with the contacts, whereby the presence of a metallic object adjacent the magnet alters the magnetic field thereof to cause an electro-motive force to be generated in the coil and thereby operate the detonator, a firing train leading from the detonator, a safety gate mounted on said cap and normally maintaining the firing train unarmed, the gate being normally held in its safe position by said projecting end of the rod and being released in response to said actuation of the rod, and means operable upon release of the gate for moving it to an armed position to arm said firing train.

6. A bomb fuze for use against a magnetic target and comprising, a magnet mounted in said fuze and having a flux path of high reluctance linking the poles externally of said magnet, a coil wound on said magnet whereby a current is induced in said coil as the fuze approaches proximity to a magnetic target, a detonator for firing said bomb, and means for electrically connecting the coil to the detonator.

7. A bomb fuze for use against a magnetic target and comprising, a magnet fixed on said fuze and having a flux path of high reluctance externally linking the poles thereof, a coil of wire in fixed linking relation with the magnet, an electrical detonator in said fuze, means including a pair of contacts for electrically connecting the coil to the detonator, bridging means for said contacts, and arming means for moving said bridging means into engagement with said contacts whereby a voltage is induced in said coil and the detonator is fired when the magnet comes into proximity with a magnetic target.

References Cited in the file of this patent UNITED STATES PATENTS 384,662 Zalinski June 19, 1888 384,663 Zalinski June 19, 1888 914,371 Davis Mar. 2, 1909 1,681,390 Bold Aug. 21, 1928 1,848,355 King Mar. 18, 1932 FOREIGN PATENTS 803,907 France July 20, 1936 525,333 Great Britain Aug. 27, 1940 

